Found this link which solves a huge memory issue when I'm using SessionSaver to keep 40 tabs open at the same time. Current memory use before implementing this as 161,680KB + 368,644KB of memory, 132 Tabs open...

"The Firefox memory leak is not a bug. It's a feature! The 'feature' is how the pages are cached in a tabbed environment." From the article: "To improve performance when navigating (studies show that 39% of all page navigations are renavigations to pages visited less than 10 pages ago, usually using the back button), Firefox 1.5 implements a Back-Forward cache that retains the rendered document for the last five session history entries for each tab. This is a lot of data. If you have a lot of tabs, Firefox's memory usage can climb dramatically. It's a trade-off. What you get out of it is faster performance as you navigate the web."

To turn this off:

Type "about:config" (no quotes) into your address bar, then scroll down to the browser.sessionhistory.max_total_viewers setting, double-click on it, then change the number to 0 and hit OK.